Deformational plagiocephaly (DP) refers to cranial asymmetry believed to be attributable to external forces molding the malleable infant skull. Suspected casual factors include pre-natal factors (e.g., intrauterine constraint), post-natal events (e.g., invariant positioning during sleep) and/or underlying neuropathology. Initial studies of the neurodevelopment of children with DP have found evidence for significant deficits, but methodological problems limit the interpretation of these studies;potential explanations for such findings are unclear. Further investigation is necessary to refine etiological hypotheses and to provide clinicians and parents with accurate information regarding the neurodevelopmental correlates of DP. Several factors indicate the need for rather immediate study of these issues: the rapidly increasing rate of DP (and/or increasing awareness of and parental worry about the condition), the proliferation of associated medical treatments (helmets and craniofacial surgery), the possibility of preventable developmental problems, and the implication of causal association with the American Academy of Pediatrics "Back to Sleep" campaign. In this 5-year longitudinal study, we would like to investigate these issues by recruiting 300 infants with DP and 325 matched controls, following them from age 6 to 36 months. A subgroup of DP cases will be imaged using MRI (n= 46) and compared to controls by sharing data with another NIH-funded study of normal brain development. Specific aims are: (1) Compare the neurodevelopment of infants/toddlers with and without DP using a multi-domain model of neuropsychological development;(2) Among infants with DP, determine the association between neurodevelopmental status and severity of cranial asymmetry (assessed by both clinical judgment and skull imaging);(3) Develop and test a predictive model of 36-month neurodevelopmental outcomes for infants with DP;(4) Evaluate the perceived facial appearance of infants with and without DP (does the condition produce noticeable effects on facial appearance, as many parents fear?);(5) Develop and test a predictive model of parent participation in elective treatments (i.e., what parent/family and infant medical factors best predict treatment participation?) and (6) Using MRI, compare the brain structure and volume of infants with and without DP;among cases, examine relations among brain structure/volume, skull asymmetry, and neuropsychological status.